How Do You Determine the Radius of a Sphere If Its Mass is Seven Times Another?

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To determine the radius of a sphere with a mass seven times greater than another, the relevant formulas are the average density equation (ρ = m/V) and the volume of a sphere (V = 4π/3 r³). The first sphere has a radius of 4.95 cm, leading to a calculated volume of 508.05 cm³. Using the mass ratio and the relationship between the radii, the radius of the second sphere is found to be approximately 9.469 cm. The calculations confirm that the radius increases with the cube root of the mass ratio. This method effectively demonstrates how to relate mass and radius in spheres of uniform density.
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I'm really bad at physics and need help with the following question:

Two spheres are cut from a certain uniform rock. One has radius 4.95 cm. The mass of the other is seven times greater. Find its radius.
 
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The average density of an object is:

\rho = \frac{m}{V}

Where m is mass and V is volume

The volume of a sphere is:

V = \frac{4\pi}{3} r^3

Where r is the radius.

These are the only two formulas you need.
 
Does this look familiar?

\frac {R_1}{R_2} = \left(\frac{M_1}{M_2}\right)^{\frac{1}{3}
 
Alright, well I got a volume of 508.05 for the sphere with a radius of 4.95, but still not exactly sure of where to go from here.
 
Okay, nevermind, I got the answer at 9.469
 

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